MIOpen OpenCL runtime backend deprecation phases

[junliume]

Since most of our known clients use the AMD HIP based backend for managing code objects and launching kernels, the MIOpen team has decided to deprecate the OpenCL backend.

• Phase 0: Add deprecation message: Add OpenCL deprecation Message #1664

[atamazov]

Let's agree that at phase 0 we do not touch OCL-backend related functionality, i.e.:

• Do to fix issues except blockers (which unlikely to happen as OCL BE testing should be removed)
• Do not implement new features for OCL BE

[artyom-beilis]

Why opencl depricated.

I'm working on PyTorch OpenCL backend that works universally on Windows and Linux, that works on nVidia, AMD (including GCN) and Intel. Integration with MIOpen could be very helpful.

Instead of making MIOpen more accessible you limit it even more...

Finally these are optimized kernels, it does not really matter what is the platform.